Apparatus and method for monitoring a system

ABSTRACT

An apparatus and method for monitoring a system or patient to provide information regarding the status of the system. The apparatus transforms measured values of more than one parameter of the system using a function dependent on at least baseline and critical values of the parameters. The apparatus further includes mapping means for mapping the function to a sequence of reference values and generating a deviation indicator for each parameter. The deviation indicators are analyzed by an analyzer to generate information concerning the status of the system or patient.

FIELD OF THE INVENTION

The present invention relates to an apparatus and a method formonitoring a system and, more specifically, to an apparatus and a methodfor monitoring a system to provide information regarding the status ofthe system.

BACKGROUND OF THE INVENTION

Many industries require that vast amounts of data pertaining to aparticular system be monitored and analyzed in order to makesplit-second assessments concerning the condition of the system. Forexample, physicians and anesthesiologists routinely monitor more thanthirty physiological parameters (e.g., heart rate, blood pressure,cardiac output, etc.) when treating patients in intensive care units,operating rooms, and emergency rooms. Also, financial advisors andanalysts in the course of their work frequently check many parametersthat can influence stock prices (e.g., closing price, 52-week high andlow, dividends, yield, change, previous day high and low, etc.) in orderto appropriately advise their clients. Further, control room operators,such as in industrial, power plant, and aviation control rooms, monitora variety of outputs to insure that the system being monitored isfunctioning properly.

Often, misdiagnosis of the condition of the system occurs because of thesheer volume of the data to be monitored. For example, in the field ofanesthesiology, anesthesiologists are surrounded by multiple vital signmonitors that display many data elements and can generate a myriad ofalarms. In the noisy and congested atmosphere surrounding an operationon a patient or in the initial period after the operation when a largenumber of patients may be monitored by a few persons, busy physiciansand nurses can miss physiological changes in the patient that arematerial to the well being of the patient. In this regard, it isestimated that in the United States, between 2,000 and 10,000 patientsdie each year from anesthesia related accidents. It is believed thatmany of these accidents could be avoided by transforming the plethora ofdata currently provided to the physician by monitors into a more usefulform that would provide an earlier indication of physiological changesin the condition of the patient.

Monitoring systems have been developed to assist users in processingvast amounts of data. For example, in the medical profession, a patientmonitoring system has been described wherein a plurality of medicalparameters are measured and transformed to provide a danger levelassociated with each parameter. The highest danger level is selected torepresent the status of the system. The transformation of the medicalparameters is performed using a function exhibiting a maximum slope forparameter values near the homeostasis level for that parameter. As thesystem is extremely sensitive to small changes in each parameter aboutthe homeostasis level of each parameter, the system can lead to falsewarnings. Also, the measurement of the highest danger level can havelimited usefulness as an indicator of the status of the system orpatient. More frequently, the user can better assess the status of thesystem or patient if the user is provided with information about theparameters not registering the highest danger or critical level andinformation about the parameter at the highest danger or critical levelbefore that parameter reached the critical level.

In light of the above, it would be advantageous to provide an apparatusand method for monitoring a system wherein an overwhelmingly largeamount of data is consolidated to provide the user with a manageableamount of information to assess the condition of the system and changesin most, if not all, of a set of measured parameters associated with thesystem. Preferably, the apparatus and method is responsive to therequirements of the user and the specific system being monitored. Inaddition, the system and method should minimize the number of falsewarnings and be rapid enough to provide information in a time frame thatis required by the user.

SUMMARY OF THE INVENTION

The disadvantages associated with the known apparatus and methods formonitoring systems are overcome by an apparatus and method in accordancewith the present invention. According to the present invention,individual measured parameters are transformed to generate one or morestatus indicators. The status indicators provide a user with valuableinformation for assessing the overall status of the system. In addition,the status indicators can be calculated on-line, in real-time, therebyproviding the user with up-to-date information so that the user mayquickly respond to problems as they arise. Further, the transformationmay be dependent upon individual characteristics of both the particularuser and the particular system being monitored. Accordingly, the userwill have an intuitive, as well as an empirical, understanding of howdecisions regarding the system will influence the transformation of thesystem.

An apparatus according to the present invention optionally comprisesphysical sensors or logical sensors, such as monitors, for measuring thevalues of a plurality of parameters associated with the system ofinterest. The specific number and types of sensors used will depend uponthe particular system being monitored. In one embodiment, the sensorsare small enough to be directly attached to the system. An example ofsuch a sensor is a temperature probe. Additionally, the sensor may be acomponent of a remote sensing station. Accordingly, the sensor cansupply measured values to the remote sensing station in either acontinuous mode or on demand. Further, the sensor or the remote sensingstation may be provided with a data storage means, such as a computerreadable disk, for storing the values measured by the sensor so that thevalues can be processed at a later time.

The sensors are connected to or incorporate a processor so that thevalues of the measured parameters are passed from the sensors to theprocessor across one or more signal lines. The processor comprises atransformer which transforms the measured value of each parameter to adeviation indicator. The transformer preferably utilizes threeparameter-dependent coefficients, such as baseline, minimum, and maximumvalues, to generate the deviation indicator corresponding to eachparameter. The parameter-dependent coefficients are preferablytransferred to the transformer from a user interface, such as a computerkeyboard, or from a data-storage means, such as a computer readabledisk. The user interface communicates with the transformer via signallines.

The deviation indicators corresponding to each parameter are then passedto an analyzer across another signal line. The analyzer analyzes orevaluates the individual deviation indicators and generates one or morestatus indicators. The status indicators represent information regardingthe overall status of the system being monitored. This information canbe provided to the user so that the user can assess the status of thesystem. Additionally, the status indicators can provide the user withinformation regarding the status of individual deviations of certainparameters comprising a subsystem of the system. Preferably, the statusindicators comprise a maximum deviation indicator, an average deviationindicator, and/or a system criticality indicator.

The present invention also relates to a method for monitoring a system.In the method according to the present invention, a user generates asystem profile. The system profile contains system-specific anduser-specific information corresponding to each of a plurality ofparameters associated with the system being monitored. Preferably theinformation indicates the baseline, minimum, and maximum values for eachparameter.

The values of each parameter are then measured. Each measured value istransformed to provide a deviation indicator for each parameter. Thedeviation indicator reflects the severity of the deviation of themeasured value from the baseline value. Preferably, the deviationindicator is an integer value between zero and five, with higher valuesindicating a more severe deviation.

The deviation indicators are analyzed in order to generate one or morestatus indicators. The status indicators provide information on thesystem or one or more subsystems concerning the overall status orchanges in the status over time. Preferably, the status indicatorsinform the user about the maximum deviation, the average deviation,and/or the system criticality.

Finally, the status indicators are presented to the user in a form whichconveys to the user the status of the system. Based on the statusindicators, the user can take appropriate action to either improve thestatus of the system or maintain the current status of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe preferred embodiments of the present invention, will be betterunderstood when read in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a schematic representation of an apparatus for monitoring asystem in accordance with the present invention;

FIG. 2 is a flow chart showing the steps involved in a method formonitoring a system in accordance with the present invention;

FIG. 3 is a flow chart showing the steps involved in a transformationstep of FIG. 2;

FIG. 4 is a flow chart showing the steps involved in an analysis step ofFIG. 2;

FIG. 5 is a graph showing a preferred function for transforming onemeasured parameter in accordance with the present invention;

FIG. 6 is a view of a display in accordance with the present inventionfor monitoring a patient wherein the patient suffers from a mildcardiovascular (CVS) problem;

FIG. 7 is a view of the display in FIG. 6 wherein the patient suffersfrom a respiratory problem (RSP) caused mainly by a decrease of thetidal volume (TV), while the cardiovascular problem persists;

FIG. 8. is a view of the display in FIG. 7 wherein the patient suffersfrom an additional cardiovascular problem caused by an increase insystolic blood pressure, while the respiratory problem persists; and

FIG. 9 is an expanded view of a parameter value display.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An apparatus 10 for monitoring a system in accordance with the presentinvention is shown schematically in FIG. 1. The apparatus 10 comprisesthree sensors 12 operatively connected to the system for measuring thevalues of three separate parameters associated with the system. However,the number and types of sensors 12 used will vary, depending upon thespecific application. For example, when the status of a patient is beingmonitored in an operating room or intensive care setting, more thanthirty different physiological parameters (e.g., heart rate, bloodpressure, cardiac output, etc.) are typically measured.

The measured values of the parameters are then transferred from a sensorto a processor 15 across one or more signal lines 14. In one embodiment,the sensors 12 are interfaced to the processor 15 using an RS-232 serialmultiplexer. The processor 15 can comprise a single stand-alone unit orit can be linked to a departmental network using client/serverarchitecture. In one embodiment, the processor 15 comprises a PC Pentiumplatform using UNIX or Windows NT operating system. Further, theprocessor 15 is developed as an object oriented implementation in theC++ language. The processor 15 uses an Ethernet Network card and runsTCP/IP communication protocol. Cables or wireless communication devicesmay be used by the network architecture.

The processor 15 optionally comprises a user interface 18 fortransferring a system profile to a transformer 16 across a signal line14. Preferably, the user interface 18 is in the form of a computerkeyboard so that the user can directly input information to thetransformer 16. Accordingly, the user interface 18 can be developedusing an OSF/MOTIF Toolkit. Alternatively, the system profile can bestored in a form which can be accessed by the transformer 16. The systemprofile supplied to the transformer 16 comprises information about thebaseline, minimum, and maximum values of each of the parameters.Identifying information about the system (i.e., system type, user'sname, identification number, time, date, etc.) can also be provided.

The transformer 16 takes the measured values of each parameter andgenerates a deviation indicator for each parameter. The transformer 16assigns to each parameter a deviation indicator which represents thelevel of danger associated with the parameter. In one embodiment, eachparameter is assigned one of six levels of danger, ranging from zero tofive according to the following scale:

0=baseline, no deviation

1=minimum deviation

2=mild deviation

3=moderate deviation

4=severe deviation

5=very severe deviation

Accordingly, the transformation maps each parameter into numbersrepresenting the state of each parameter relative to the system'shomeostatic conditions (i.e., baseline values for each parameter) and toprescribed maximum and minimum reference values for each parameter.

The individual deviation indicators are then transferred across a signalline 14 to an analyzer 20. The analyzer 20 analyzes or evaluates thevalues of the deviation indicators and generates one or more statusindicators. The status indicators contain information regarding theoverall status of the system. In one embodiment, the analyzer 20analyzes the individual deviation indicators to each other to determinethe maximum deviation indicator, the average indicator, and/or thesystem criticality.

A display unit 22 is provided for communicating the status indicators tothe user. The display unit 22 is connected to the analyzer 20 by asignal line 14 which allows the status indicators to be passed from theanalyzer 20 to the display unit 22. Preferably, the display unit 22comprises a video monitor so that the status indicators can be visuallydisplayed in a form that is easily analyzed by the user.

The present invention also relates to a method, such as acomputer-controlled method, for monitoring a system as depicted in FIG.2. According to the method, a system profile is generated at step 50.The user is given an option of either creating a new system profile orrecalling an old one. If a new system profile is to be created, the userinputs information regarding the parameters to be monitored. For mostapplications, such information includes the number and types ofparameters to be monitored and a baseline, a minimum, and a maximumvalue for each parameter. If, however, an old system profile is to beused, the user is preferably given an option to adjust the existingsystem profile. Accordingly, the user may change the number and/or typesof parameters to be monitored or alter the baseline, minimum, or maximumvalues associated with the parameters.

The system profile may be generated by inputting information into thesystem 10 with a user interface 18, such as a computer keyboard. Formost applications, the minimum and maximum values for the parameterswill be the same for similar types of systems. However, the baselinevalues are likely to differ from system to system, even for similarsystems. Accordingly, the method of the present invention allows theuser to tailor the system profile to the individual characteristics ofthe system to be monitored.

Once the system profile has been generated, the values of the individualparameters are measured at step 52. The number of parameters that shouldbe measured will vary from system to system and application toapplication. However, the method of the present invention is completelyapplicable to the measurement of any number of parameters.

At step 54, the measured value of each parameter is transformed to yielda deviation indicator for each parameter. Preferably, the measuredvalues are mapped into a corresponding deviation indicator using atransformation function which has a minimum sensitivity for deviationsclose to the baseline value of the parameter. Also, the function ispreferably asymmetric about the baseline value to provide the user withgreater flexibility. Toward that end, the function reflects theinformation regarding the parameters which was generated as part of thesystem profile at step 50.

The process for transforming each measured value into a deviationindicator at step 54 is shown in greater detail in FIG. 3. A mappingparameter is generated for each parameter at step 55. The form of themapping parameter is determined by the function used to effectuate thetransformation. The mapping parameter reflects the information regardingeach parameter which was generated as part of the system profile at step50. Preferably, the mapping parameter is different for values of theparameter above the baseline value and below the baseline value.

Once the value of the mapping parameter has been determined, the mappedvalue of the parameter is generated at step 57. The mapped value isgenerated using the transformation function and the appropriate valuefor the mapping parameter.

The mapped value of each parameter is then used to generate thedeviation indicator for each parameter at step 59. The deviationindicator is determined by assigning to each parameter a level of dangerassociated with the parameter. Preferably, the higher the mapped value,the higher the level of danger. In one embodiment, each mapped value isassigned one of six levels o f danger, ranging from zero to fiveaccording to the following scale:

0=baseline, no deviation

1=minimum deviation

2=mild deviation

3=moderate deviation

4=severe deviation

5=very severe deviation.

In one particular embodiment, the equation used to transform themeasured values of the parameters to the deviation indicators is of thefollowing form:

    y=1/2{1-exp(-M(x-x.sub.b1).sup.2)},

wherein y represents the value of the function, x represents themeasured value of the parameter, x_(b1) represents the baseline valuefor the parameter, and M represents the mapping parameter.

The mapping parameter, M, is determined by solving the above equation interms of M. Accordingly, the mapping parameter is given by an equationof the form: ##EQU1## The mapping parameter, M, is then solved for tworanges of the parameter, x. The first range corresponds to values of xwhen x<x_(b1) and the second range corresponds to values of x whenx≧x_(b1). Alternatively, the first range corresponds to values of x whenx≦x_(b1) and the second range corresponds to values of x when x>x_(b1).Accordingly, the two values of the mapping parameter corresponding tothe two ranges are given by the following equations: ##EQU2## and##EQU3## wherein y' represents the value of the function at x_(min),x_(min) represents the minimum value of the parameter, y" represents thevalue of the function at x_(max), and x_(max) represents the maximumvalue of the parameter.

Once the values of the mapping parameter, M, for the two ranges havebeen determined, the mapped value of the parameter is generated using anequation of the form:

    y=1/2{1-exp(-M.sub.min (x-x.sub.b1).sup.2)}, for x<x.sub.b1.

     1/2{1-exp(-M.sub.max (x-x.sub.b1).sup.2)}, for x≧x.sub.b1

For each parameter, the measured value of the parameter, x, is pluggedinto the above equation, along with the appropriate baseline value,x_(b1), and mapping parameter, M. Accordingly, a mapped value of eachparameter, y, is generated.

The mapped value of each parameter, y, is then used to generate thedeviation indicator for each parameter using an equation of the form:

    DI=.left brkt-bot.K×y.right brkt-bot.

wherein DI represents the deviation indicator, K represents a constant,y represents the value of the function, and ".left brkt-bot. .rightbrkt-bot." represents a floor function that returns the largest integervalue of an expression contained between the ".left brkt-bot." and the".right brkt-bot." symbols.

A graph of a representative function for transforming the heart rate ofa patient is shown in FIG. 5. When monitoring the heart rate of a humanpatient, a minimum of 40 BPM (beats per minute) and a maximum of 160 BPMis generally applicable. Although the baseline value of the heart ratewill vary from patient to patient, a baseline value of 80 BPM could beconsidered normal for some patients. Accordingly, if we want torepresent the deviation indicator one of six danger levels, we canassign the function at the minimum and maximum, y' and y", a value of0.4 and the constant K a value of 12.5. As a result, M_(min) is 0.001006and M_(max) is 0.000251. Therefore, if the heart rate is measured to be60 BPM, the deviation indicator is determined to be 3. Similarly, if theheart rate is measured to be 100 BPM, the deviation indicator isdetermined to be 1. It is readily apparent from those values that thesame magnitude shift results in a higher deviation indicator when theheart rate is lower than the baseline value than when the heart rate ishigher than the baseline value.

Returning to FIG. 2, once the deviation indicators have been determinedfor each parameter, the deviation indicators are analyzed to generateone or more status indicators at step 61. The status indicators containinformation about the overall status of the system.

The steps involved in generating the status indicators at step 61 areshown in more detail in FIG. 4. A maximum deviation indicator isdetermined at step 62 using an equation of the form:

    DI.sub.max =max{DI.sub.i |i=1, . . . , n}

wherein n is the total number of parameters being measured and max{ . .. } is a function which returns the maximum value of the elementsenclosed between the "{" and the "}".

In addition, an average deviation indicator is determined at step 64using an equation of the form: ##EQU4## wherein y_(i) is the mappedvalue of the i^(th) parameter and n is the total number of parametersbeing measured.

Further, system criticality is determined at step 66 using an equationof the form: ##EQU5## wherein n_(m) is the total number of parameterswith a deviation indicator, DI, equal to DI_(max).

In addition, one or more subsystems can be defined wherein the measuredparameters are grouped according to subsystems. For a patient monitoringsystem, typical subsystems may include respiratory (RSP), centralnervous system (CNS), and cardiovascular (CVS) subsystems. In someapplications, the same parameter can be grouped in more than onesubsystem. One or more subsystem status indicators associated with eachsubsystem are then generated at step 67 by analyzing the deviationindicators for the measured parameters which are grouped in eachsubsystem. The subsystem status indicators comprise the largestdeviation indicator of all the parameters grouped in that subsystem.Alternatively, the subsystem status indicator can comprise the averageof the deviation indicators for the parameters grouped in thatsubsystem. Also, the subsystem status indicator can comprise thesubsystem criticality, which is determined in an analogous manner to thesystem criticality described above.

Returning to FIG. 2, after the status indicators have been generated atstep 61, the status indicators are displayed in a display window 24 atstep 68. An example of the display window 24 for displaying the statusindicators is shown in FIGS. 6-8. The display window 24 in the figuresis particularly designed for the medical monitoring of a patient.However, the display window 24 can be customized to adapt to thespecific needs of the user and the type of system being monitored, suchas the stock market. The display window 24 is preferably updated aboutonce per second or faster. However, the display window 24 can be updatedat any preselected time interval. Accordingly, the essentiallycontinuous analysis helps detect and highlight even the most subtlechanges before they become critical.

A short term display 25 established for a fixed period of time isprovided for displaying a graph of the maximum deviation indicator andthe average deviation indicator as a function of time. Preferably, theshort term display 25 displays the value of the maximum and averagedeviation indicators over a specific or fixed time period. The shortterm display 25 preferably scrolls from right to left so that the fixedtime period is always being displayed.

A long term display 30 that can be modified by the user is preferablyprovided. The long term display 30 is essentially identical to the shortterm display 25 except that the long term display 30 displays the valuesover a longer time period than the short term display and, as notedabove, the time period displayed can be modified.

A parameter value display 32 can also be provided to display themeasured value of one or more parameters as a function of time. Thevalues of the parameters are plotted as a graph 36 of the value as afunction of time. Preferably, the user is able to select whichparameters are displayed. In the embodiment shown in FIGS. 6-8, thevalues for three different parameters are graphed, 36, 136, and 236,simultaneously on the same plot. The identity of the parameters beingdisplayed are indicated by the parameter identifiers 34, 134, and 234.The parameter value display 32 also comprises parameter statisticsindicators, 38, 138, and 238, which provide the current measured valuesand the baseline, minimum, and maximum values for each parameter beingdisplayed. Color coding can be used to inform the user which graph 36and parameter statistics indicator 38 corresponds to each parameterbeing graphed. Accordingly, as best shown in FIG. 9, the graph 36 andparameter statistics indicator 38 are preferably displayed in the samecolor as the parameter identifier 34. Similarly, graph 136 and indicator138 are preferably displayed in the same color as identifier 134 andgraph 236 and indicator 238 are preferably displayed in the same coloras identifier 234.

The display window 24 can also comprise a subsystem alarm display 40.The subsystem alarm display 40 provides the user with importantinformation regarding the parameters being measured. The subsystem alarmdisplay 40 displays the subsystem status indicator which indicates thedegree of deviation associated with each subsystem. Preferably, thedegree of deviation is indicated by assigning different colors to thedifferent degrees of deviation and displaying the subsystem alarmdisplay 40 for each subsystem in the appropriate color. In oneembodiment, the degrees of deviation are assigned colors ranging fromwhite for no deviation to red for a very severe deviation. Theintermediate degrees of deviation are assigned colors of varying shadesof yellow and orange. In addition to the visual warning, an audio outputcan be provided to indicate the degree of deviation. In one embodiment,the audio output varies in pitch as the degree of deviation increases,thereby alerting the user.

In addition, the user can be given the option to view the particularparameters which contribute to the subsystem status indicator. As shownin FIGS. 7 and 8, the parameter deviation display 42 for the parameterswhich are contributing to the subsystem status indicator are displayedto the right of the subsystem status indicator. The color of theparameter deviation display 42 corresponds to the degree of deviationassociated with the deviation indicator for that parameter. An up ordown arrow is also displayed to indicate whether the measured value ofthe parameter has shifted above or below the baseline value for thatparameter.

A sensor status display 44 can also be provided, as shown in FIG. 7. Thesensor status display 44 indicates to the user either when a new sensorhas started to function or when a sensor which was functioning ceases tofunction properly. The sensor status display 44 is particularly usefulto alert the user that a sensor has been disconnected from the system.

A causal display 46 can also be provided. The casual display 46 ishighlighted when a parameter changes from its baseline value to apredefined level or higher and remains at that level or higher for aminimum time. For example, the display 46 can be highlighted when thedeviation indicator of a parameter changes from zero to two or higherand remains at a level of two or higher for more than about two minutes.The display 46 is highlighted by changing its color from a backgroundcolor, such as grey, to a color which indicates a warning, such asorange. In one embodiment, when the causal display 46 is highlighted,information relating to the parameters which have contributed to thecausal display 46 being highlighted appears in tabular form at therequest of the user. Further, the indicator 46 preferably indicates themost recent event preceding the deviation.

The display window 24 may also comprise an unstable parameter display49. The unstable parameter display 49 is highlighted whenever thesensors identify a parameter that deviates by two or more levels on thescale. The display 49 is highlighted by changing its color from abackground color, such as grey, to a color which indicates a warning,such as orange. The display 49 remains highlighted as long as theparameter does not stabilize, i.e., continues to rise or fall on thescale.

Further, the display window 24 optionally comprises an event display 47.The event display 47 allows the user to record the occurrence of eventsso that the systems response to such events can be monitored. Theoccurrence of an event is recorded by the user by selecting theparticular event which has occurred from an event selector 48.Preferably, the event selector 48 comprises a number of user selectableicons which are selected by clicking on the appropriate icon with acomputer mouse. The occurrence of the event is then registered on theevent display 47 indicating the time at which the event occurred.

The criticality indicator 45 combines both the average deviation of allthe parameters being monitored and the number of parameters thatcontribute to the maximum deviation. This indicator 45 is displayed tothe user upon request by selecting a time point from the time framewindow or by selecting the criticality trend from a review utility 39.

The review utility 39 can be provided to allow the user to review thehistory status of the system at any selected time, from the time thatthe monitoring of the system began until the present time. In oneembodiment, the review utility 39 is accessed by selecting an icon whichappears on the display window 24 using a computer mouse.

Returning to FIG. 2, after the status indicators have been displayed atstep 68, it is determined whether new values for the parameters are tobe measured at step 70. If new values are to be measured, the methodreturns to step 52. However, if no new values are to be measured, themethod proceeds to step 72, where the method stops.

The apparatus 10 and method of the present invention are useful in awide range of applications. The ability of the user to monitor aplurality of parameters and identify problems at an early stage makesthe invention particularly suited for examining patients in intensivecare units, operating rooms, and emergency rooms; analyzing financialdata associated with, for example, the stock market; monitoringparameters associated with control rooms, such as those used inindustry, aviation, and power stations; and checking parametersassociated with the automotive industry, in the manufacturing of carsand/or in the diagnosis of individual cars.

However, it will be recognized by those skilled in the art that changesor modifications may be made to the above-described embodiments withoutdeparting from the broad inventive concepts of the invention. It shouldtherefore be understood that this invention is not limited to theparticular embodiments described herein, but is intended to include allchanges and modifications that are within the scope and spirit of theinvention as set forth in the claims.

What is claimed is:
 1. An apparatus for monitoring a systemcomprising:a. means for sensing a plurality of parameters associatedwith the system; b. transformation means for transforming each value ofsaid plurality of parameters associated with the system using a functiondependent on at least baseline and critical values of the parameter,wherein the transformation means employs a function which exhibits aminimum sensitivity for deviations close to the baseline value of theparameter of a form:

    y=1/2{1-exp(-M(x-x.sub.b1).sup.2)},

wherein y represents a value of the function, x represents a measuredvalue of the parameter, x_(b1) represents the baseline value for theparameter, and M represents a mapping parameter such that ##EQU6## and##EQU7## wherein y' represents a value of the function at x_(min),x_(min) represents a minimum value of the parameter, y" represents avalue of the function at x_(max), and x_(max) represents a maximum valueof the parameter; c. mapping means for mapping the function to asequence of reference values and generating a deviation indicator foreach parameter; and d. analysis means for analyzing the deviationindicators and generating an average deviation indicator.
 2. Anapparatus for monitoring a system comprising:a. means for sensing aplurality of parameters associated with the system; b. transformationmeans for transforming each value of said plurality of parametersassociated with the system using a function dependent on at leastbaseline and critical values of the parameter, wherein thetransformation means employs a sigmoid function; c. mapping means formapping the function to a sequence of reference values and generating adeviation indicator for each parameter; and d. analysis means foranalyzing the deviation indicators and generating an average deviationindicator.
 3. An apparatus for monitoring a system comprising:a. meansfor sensing a plurality of parameters associated with the system; b.transformation means for transforming each value of said plurality ofparameters associated with the system using a function dependent on atleast baseline and critical values of the parameter; c. mapping meansfor mapping the function to a sequence of reference values andgenerating a deviation indicator for each parameter, wherein the mappingmeans comprises a means for determining the deviation indicatorsemploying a function of a form:

    DI=.left brkt-bot.K×y.right brkt-bot.

wherein DI represents the deviation indicator, K represents a constant,y represents a value of the function, and ".left brkt-bot. .rightbrkt-bot." represents a floor function that returns a largest integervalue of an expression contained between the ".left brkt-bot." and the".right brkt-bot." symbols; and d. analysis means for analyzing thedeviation indicators and generating an average deviation indicator. 4.An apparatus for monitoring a system comprising:a. means for sensing aplurality of parameters associated with the system; b. transformationmeans for transforming each value of said plurality of parametersassociated with the system using a function dependent on at leastbaseline and critical values of the parameter, wherein thetransformation means employs a function which exhibits a minimumsensitivity for deviations close to the baseline value of the parameterof a form:

    y=1/2{1-exp(-M(x-x.sub.b1).sup.2)},

wherein y represents a value of the function, x represents a measuredvalue of the parameter, x_(b1) represents the baseline value for theparameter, and M represents a mapping parameter such that ##EQU8## and##EQU9## wherein y' represents a value of the function at x_(min),x_(min) represents a minimum value of the parameter, y" represents avalue of the function at x_(max), and x_(max) represents a maximum valueof the parameter; c. mapping means for mapping the function to asequence of reference values and generating a deviation indicator foreach parameter; and d. analysis means for analyzing the deviationindicators and generating a system criticality indicator.
 5. Anapparatus for monitoring a system comprising:a. means for sensing aplurality of parameters associated with the system; b. transformationmeans for transforming each value of said plurality of parametersassociated with the system using a function dependent on at leastbaseline and critical values of the parameter, wherein thetransformation means employs a sigmoid function; c. mapping means formapping the function to a sequence of reference values and generating adeviation indicator for each parameter; and d. analysis means foranalyzing the deviation indicators and generating a system criticalityindicator.
 6. An apparatus for monitoring a system comprising:a. meansfor sensing a plurality of parameters associated with the system; b.transformation means for transforming each value of said plurality ofparameters associated with the system using a function dependent on atleast baseline and critical values of the parameter; c. mapping meansfor mapping the function to a sequence of reference values andgenerating a deviation indicator for each parameter, wherein the mappingmeans comprises a means for determining the deviation indicatorsemploying a function of a form:

    DI=.left brkt-bot.K×y.right brkt-bot.

wherein DI represents the deviation indicator, K represents a constant,y represents a value of the function, and ".left brkt-bot. .rightbrkt-bot." represents a floor function that returns a largest integervalue of an expression contained between the ".left brkt-bot." and the".right brkt-bot." symbols; and d. analysis means for analyzing thedeviation indicators and generating a system criticality indicator. 7.An apparatus for monitoring a system comprising:a. means for sensing aplurality of parameters associated with the system; b. transformationmeans for transforming each value of said plurality of parametersassociated with the system using a function dependent on at leastbaseline and critical values of the parameter, wherein the functionexhibits a minimum sensitivity for deviations close to the baselinevalue of the parameter, wherein the transformation means employs afunction of a form:

    y=1/2{1-exp(-M(x-x.sub.b1).sup.2)},

wherein y represents a value of the function, x represents a measuredvalue of the parameter, x_(b1) represents the baseline value for theparameter, and M represents a mapping parameter such that ##EQU10## and##EQU11## wherein y' represents a value of the function at x_(min),x_(min) represents a minimum value of the parameter, y" represents avalue of the function at xmax, and x_(max) represents a maximum value ofthe parameter; and c. mapping means for mapping the function to asequence of reference values and generating a deviation indicator foreach parameter.
 8. An apparatus for monitoring a system comprising:a.means for sensing a plurality of parameters associated with the system;b. transformation means for transforming each value of said plurality ofparameters associated with the system using a function dependent on atleast baseline and critical values of the parameter, wherein thefunction exhibits a minimum sensitivity for deviations close to thebaseline value of the parameter; and c. mapping means for mapping thefunction to a sequence of reference values and generating a deviationindicator for each parameter, wherein the mapping means comprises ameans for determining the deviation indicators employing a function of aform:

    DI=.left brkt-bot.K×y.right brkt-bot.

wherein DI represents the deviation indicator, K represents a constant,y represents a value of the function, and ".left brkt-bot. .rightbrkt-bot." represents a floor function that returns a largest integervalue of an expression contained between the ".left brkt-bot." and the".right brkt-bot." symbols.
 9. A method for monitoring a systemcomprising:a. a sensing step for sensing a plurality of parametersassociated with the system; b. a transformation step for transformingeach value of said plurality of parameters associated with the systemusing a function dependent on at least baseline and critical values ofthe parameter, wherein the transformation step employs a function whichexhibits a minimum sensitivity for deviations close to the baselinevalue of the parameter of a form:

    y=1/2{1-exp(-M(x-x.sub.b1).sup.2)},

wherein y represents a value of the function, x represents a measuredvalue of the parameter, x_(b1) represents the baseline value for theparameter, and M represents a mapping parameter such that ##EQU12## and##EQU13## wherein y' represents a value of the function at x_(min),x_(min) represents a minimum value of the parameter, y" represents avalue of the function at x_(max), and x_(max) represents a maximum valueof the parameter; c. a mapping step for mapping the function to asequence of reference values and generating a deviation indicator foreach parameter; and d. an analysis step for analyzing the deviationindicators and generating an average deviation indicator.
 10. A methodfor monitoring a system comprising:a. a sensing step for sensing aplurality of parameters associated with the system; b. a transformationstep for transforming each value of said plurality of parametersassociated with the system using a function dependent on at leastbaseline and critical values of the parameter, wherein thetransformation step employs a sigmoid function; c. a mapping step formapping the function to a sequence of reference values and generating adeviation indicator for each parameter; and d. an analysis step foranalyzing the deviation indicators and generating an average deviationindicator.
 11. A method for monitoring a system comprising:a. a sensingstep for sensing a plurality of parameters associated with the system;b. a transformation step for transforming each value of said pluralityof parameters associated with the system using a function dependent onat least baseline and critical values of the parameter; c. a mappingstep for mapping the function to a sequence of reference values andgenerating a deviation indicator for each parameter, wherein the mappingstep comprises the step of determining the deviation indicatorsemploying a function of a form:

    DI=.left brkt-bot.K×y.right brkt-bot.

wherein DI represents the deviation indicator, K represents a constant,y represents a value of the function, and ".left brkt-bot. .rightbrkt-bot." represents a floor function that returns a largest integervalue of an expression contained between the ".left brkt-bot." and the".right brkt-bot." symbols; and d. an analysis step for analyzing thedeviation indicators and generating an average deviation indicator. 12.A method for monitoring a system comprising:a. a sensing step forsensing a plurality of parameters associated with the system; b. atransformation step for transforming each value of said plurality ofparameters associated with the system using a function dependent on atleast baseline and critical values of the parameter, wherein thetransformation step employs a function which exhibits a minimumsensitivity for deviations close to the baseline value of the parameterof a form:

    y=1/2{1-exp(-M(x-x.sub.b1).sup.2)},

wherein y represents a value of the function, x represents a measuredvalue of the parameter, x_(b1) represents the baseline value for theparameter, and M represents a mapping parameter such that ##EQU14## and##EQU15## wherein y' represents a value of the function at x_(min),x_(min) represents a minimum value of the parameter, y" represents avalue of the function at x_(max), and x_(max) represents a maximum valueof the parameter; c. a mapping step for mapping the function to asequence of reference values and generating a deviation indicator foreach parameter; and d. an analysis step for analyzing the deviationindicators and generating a criticality indicator.
 13. A method formonitoring a system comprising:a. a sensing step for sensing a pluralityof parameters associated with the system; b. a transformation step fortransforming each value of said plurality of parameters associated withthe system using a function dependent on at least baseline and criticalvalues of the parameter; c. a mapping step for mapping the function to asequence of reference values and generating a deviation indicator foreach parameter, wherein the mapping step comprises a step of determiningthe deviation indicators employing a function of a form:

    DI=.left brkt-bot.K×y.right brkt-bot.

wherein DI represents the deviation indicator, K represents a constant,y represents a value of the function, and ".left brkt-bot. .rightbrkt-bot." represents a floor function that returns a largest integervalue of an expression contained between the ".left brkt-bot." and the".right brkt-bot." symbols; and d. an analysis step for analyzing thedeviation indicators and generating a criticality indicator.
 14. Amethod for monitoring a system comprising:a. a sensing step for sensinga plurality of parameters associated with the system; b. atransformation step for transforming each value of said plurality ofparameters associated with the system using a function dependent on atleast baseline and critical values of the parameter, wherein thefunction exhibits a minimum sensitivity for deviations close to thebaseline value of the parameter, wherein the transformation step employsa function of a form:

    y=1/2{1-exp(-M(x-x.sub.b1).sup.2)},

wherein y represents a value of the function, x represents a measuredvalue of the parameter, x_(b1) represents the baseline value for theparameter, and M represents a mapping parameter such that ##EQU16## and##EQU17## wherein y' represents a value of the function at x_(min),x_(min) represents a minimum value of the parameter, y" represents avalue of the function at x_(max), and x_(max) represents a maximum valueof the parameter and c. a mapping step for mapping the function to asequence of reference values and generating a deviation indicator foreach parameter.
 15. A method for monitoring a system comprising:a. asensing step for sensing a plurality of parameters associated with thesystem; b. a transformation step for transforming each value of saidplurality of parameters associated with the system using a functiondependent on at least baseline and critical values of the parameter,wherein the function exhibits a minimum sensitivity for deviations closeto the baseline value of the parameter; and c. a mapping step formapping the function to a sequence of reference values and generating adeviation indicator for each parameter, wherein the mapping stepcomprises a step of determining the deviation indicators employing afunction of a form:

    DI=.left brkt-bot.K×y.right brkt-bot.

wherein DI represents the deviation indicator, K represents a constant,y represents a value of the function, and ".left brkt-bot. .rightbrkt-bot." represents a floor function that returns a largest integervalue of an expression contained between the ".left brkt-bot." and the".right brkt-bot." symbols.